BIO 1140 Lecture Notes - Lecture 17: Signal Recognition Particle, Signal Peptidase, Cytosol
Document Summary
Bio - lec 17 - translation and protein sorting. Soluble protein (that will remain in the cytosol) will be translated using free cytosolic ribosomes. Temporarily blocks translation before it docks the ribosome to the er membrane co translation (secreted) : Import protein across the membrane as its being translated. Ribosomes are in cytosol, get them to the rough er. Beginning sequence of peptide (signal seqeuncing), used to recognize that these proteins are part of the membrane. Signal recognition particle (in cytosol), looks for beacon (signal sequences as they"re extending from the ribosome), and they bind to them. So that once translation resumes, it grows through the pore into the er. Signal peptidase : signal peptidase cleaves the signal sequence peptide from the growing polypeptide and will be available to co-translate another protein, leaving you with the actual protein. Translation of the mrna complete; ribosomal subunits are recycled. Result : polypeptide free inside the er lumen.